The present invention relates to a writable optical disc, and a reading system and a manufacturing method of the disc.
In a writable optical disc, information such as a synchronizing signal and address information (hereinafter called prepit information) for searching a position on the disc are previously recorded by laser cutting at a preformat stage in a manufacturing process. As one of the methods of the preformat of the prepit information, a track (groove or land) on which information is written by a user is wobbled. In another method, prepits are recorded on the track.
However, in the former method, the track itself is wobbled in a waveform in right and left by a wobbling signal. Therefore, the magnitude of the modulation by the wobbling signal is limited to a small degree. As a result, the C/N (carrier to noise ratio) decreases. Furthermore, since the interference of the adjacent tracks at the wobbling must be considered, pitch between the tracks can not be reduced. Consequently, the writing capacity of the disc is limited.
In the latter method, since the prepits are recorded, the space for writing the information is reduced. Therefore, the available efficiency of the disc is low.